Arrangement for adjusting the position of the dead center in machine tools



Nov. 18, 1958 H. R. BRUET 2,860,538

ARRANGEMENT FOR ADJUSTING THE POSITION OF THE DEAD CENTER IN MACHINE TOOLS Filed July 24, 1957 z/sheetsaheet 1 lNVENTOR HZ-WR/ Rf/Wf BRUET 6 ATTOR/YE ys Nov. 18, 1958 H. R. BRUET 2,360,533 ARRANGEMENT FOR ADJU" NG THE POSITION OF THE DEAD CENTER MACHINE TOOLS Filed July 24, 1957 2 Sheets-Sheet 2 Fig.5

n i T: hilt; i g f 21 I 2o fi INVENTOR MWOZZ ATTORNEYS United States Patent() ARRANGEMENT FOR ADJUSTING THE POSITION OF THE DEAD CENTER IN MACHINE TOOLS Henri Ren Bruet, Paris, France, assignor of one-half to Societe Anonyme dite: Etablissements A. Cazeneuve, La Plaine Saint-Denis (Seine), France, a French com- P y Application July 24, 1957, Serial No. 673,964

Claims priority, application France August 10, 1956 Claims. (CI. 82-31) The present invention has for its object a method foradjusting the dead center generally used in machine tools and more particularly in lathes.

The means generally used for such an adjustment require the use of a shoe fitted over the bed of the machine tool, the dead center being thenafter fitted, guided and held on said shoe through any known means.

The vertical adjustment is obtained through a fitting and filing of the shoe or of the dead center and more generally of both said parts. The horizontal adjustment is obtained through a shifting of the dead center over the shoe through the agency of suitable means.

This arrangement which is of a conventional type includes two large superposed members, which leads to a lack of rigidity and of stability; its execution requires for an accurate result an expensive fitting operation so that the two parts when juxtaposed in a properly defined relative position may form a unit.

In addition to these serious defects, these prior adjusting means require numerous parts and lead to the use of a comparatively large weight of material and consequently this dead center forms an expensive article of manufacture.

The arrangement according to the invention cuts out these drawbacks and leads to important advantages both from the standpoint of rigidity and stability and from the standpoint of the easy execution, simplicity, convenience in use and accurate operation; furthermore, its execution provides a substantial economy of material and of labour.

The arrangement disclosed by way of example includes a dead center body forming a unit bearing directly on the bed of the machine and in said unit is slidably carried a barrel provided with a frusto-conical bore extending in parallelism with and eccentrically with reference to the axis of the barrel, the eccentricity extending preferably heightwise, and the dead center being carried inside said bore; said bored barrel is furthermore provided with a suitably shaped groove and it is guided in its longitudinal movements by a key engaging said groove, "and its angular shifting and its locking are obtained through a set of screws whereby the barrel is controlled so as to rock by a sufficient amount which brings the dead center by reason of its eccentricity into the accurate desired align ment.

This arrangement provides furthermore other advantages to be disclosed hereinafter.

The following description and accompanying drawings illustrating by way of example and by no means in a limiting sense the application of the invention to a lathe will allow the improved arrangement to be properly understood. In said drawings:

Fig. 1 is a front view, partly sectional, of the dead center of a lathe.

Fig. 2 is a diagrammatic showing of the means controlling the angular setting of the barrel with a view to obtaining the desired alignment of the dead center.

2,860,538 Patented Nov. 18, 1958 ICC 3 which is provided with a frusto-conical bore 4 the axis of which is parallel with the axis of the barrel and lies above said axis from which it is spaced by a height e.

Inside said conical bore 4 is fitted the actual dead center 5 adapted to carry a tool such as a drill. In the outer surface of the barrel 3 is cut a groove 6 extending in parallelism with the axis of the barrel, said groove assuming a part cylindrical shape for engagement by a key 7 of a corresponding shape and of a suitable length, said key being held without any substantial clearance in contact with the groove 6 through the agency of a radial screw 8 which engages a tapped member 8' rigid with the block 1 so as to urge the key 7 towards the barrel. as provided by the part spherical end of the screw 8 engaging the outer edge of the key 7. This key 7 is further-v more held laterally between two screws 10 and 11 screwed into the block 1 forming the body of the back center and engaging the sides of the key. Thus, it is possible to adjust the alignment of the axis of the frusto-conical bore 4 and consequently of the dead center in a horizontal plane, this being provided as will appear readily from inspection of Figs. 1 and 2.

If the axis of the dead center is to be shifted, say towards the left hand side by an amount d, the screw 8.

and the screw 11 are released in succession after which the screw 10 is screwed inwardly to make the key 7 rock round the center of the part spherical end 9 of the screw 8 which results in an angular shifting of the barrel 3 from its position 14 into its position 15 and thereby in a shifting of the axis of the back center 5 from 16 towards 17 (Fig. 2), the distance between 16 and 17 being equal to the value :1 which it is assumed is required for the obtention of the desired setting of the dead center. The

screw 8 is then screwed back so as to urge the key 7 7 without any substantial clearance inside the groove 6 and the key 7 is finally locked in its adjusted position through a fastening of the screw 11.

The barrel 3 may then slide longitudinally inside the 'block 1 while it is held in its adjusted angular position by the key 7 engaging the groove 6; thus the dead center 5 is held in the desired alignment.

In the case where the correction of the alignment be executed towards the right hand side, the operationjis similar and performed in the reverse manner.

An eccentricity e of the dead center by a comparatively small value is sufficient for obtaining a sufficientcorrecment is of a small amplitude "and consequently the ecce tricity will lead to an exceedingly small modificatio' height -as a result of horizontal shifting. By way stea ample and for an eccentricity e equal to 3 mm., a correction of alignment to the left or to the right d equal to 0.15 mm. i. e. to 0.3 mm. altogether, is sufficient in most cases and the resulting modification in height will be less than 0.008 mm. which is well within the allowances for the dead center according to standards.

It is apparent that, as a consequence of the improved arrangement described, the adjustment as to alignment is a speedy, convenient and extremely accurate matter. This correction in alignment remains unaltered during the allowed longitudinal movement of the barrel 3 sliding inside a bore which through its actual execution is per- 2,860,538 I V V a 3 fectly parallel with the shifting of the body of the dead center 1 over the bed 2 of the lathe. On the otherhand, the rigidity of the system is at a maximum since the body of the dead center forms a single block and it may be fastened directly without any intermediate member to'the surface of the bed 2 of the lathe.

;Fig. 3 shows the eccentric frusto-conical bore opening partly with a slight relative eccentricity into a bore 20 coaxial with the barrel 3; the diameter of said bore 20 is such that it allows the engagement into it of the fiat shank 21 of a tool such as a drill 22 fitted inside the frustoconical bore 4 so that said drill or the like tool may be positively held against rotation through said engagement of its shank.

Obviously, the above described arrangements are disclosed solely by way of an exemplification and they may be subjected to manymodifications and incorporate auxiliary devices chiefly as concerns the means controlling the angular setting of the barrel without unduly widening thereby the scope of the invention as defined in the accompanying claims:

What I claim is:

1. An arrangement for adjusting the position of the dead center of a machine tool provided with a bed, comprising a dead center body adapted to be rigidly and directly secured to the bed of the machine-tool, a barrel slidingly fitted in said body and the axis of which is parallel with that of said bed, a frusto-conical eccentric bore being provided in said barrel to carry the dead center, said sliding barrel being provided furthermore with a longitudinal groove, a fiat key slidingly engaging said groove, and projecting radially out of the latter, aligned screws located to either side of the key perpendicularly thereto and the tips of which are in contact with the opposite sides of the key, the movements of the screws in either direction by equal and opposite amounts shifting the key laterally and thereby urging the barrel into an angular rotation by a small amount and holding it fast in the angular position assumed by it.

2. An arrangement for adjusting the position of the dead center of a machine tool provided with a bed, comprising a dead center body adapted to be rigidly and directly secured to the bed of the machine-tool, a barrel slidingly fitted in said body and the axis of which is parallel with that of said bed, a frusto-conical eccentric bore being provided in said barrel to carry the dead center, me ns of which bore is located slightly above the axis of the barrel, said sliding barrel being provided furthermore with a longitudinal groove, a flat key slidingly engaging said groove, and projecting radially out of the lat ter, aligned screws located to either side of the key perpendicularly thereto and the tips of which are in contact wit h the opposite sides of the key, the movements of the screwsin either direction by equal and opposite amounts shifting the key laterally and thereby urging the barrel into an angular rotation by a small. amount and holding it fast in the angular position assumed by it.

3. An arrangement for adjusting the position of the dead center of a machine-tool provided with a bed, comprising a dead center body adapted to be rigidly and directly secured to the bed of the machine-tool, a barrel slidingly fitted in said body and the axis of which is parallel with that of said bed, a frusto-conical eccentric bore being provided in said barrel to carry the dead center,

the axis of which bore is located slightly above the axis of the barrel, said sliding barrel being provided furthermore with a longitudinal groove, a flat key slidingly engaging said groove, and projecting radially out of the latter, aligned screws located to either side of the key perpendicularly thereto and the tips of which are in contact with the opposite sides of the key, the movement of the screws in either direction by equal and opposite amounts shifting the key laterally and thereby urging the barrel into an angular rotation by a small amount and holding it fast in the angular position assumed by it, and a third screw engaging the dead center body and the axis of which crosses the axis of the barrel, said third screw including a part spherical head engaging the outer edge of the key to urge said key into engagement with the groove in the barrel.

4. An arrangement for adjusting the position of the dead center of a machine-tool provided with a bed, comprising a dead center body adapted to be rigidly and directly secured to the bed of the machine-tool, a barrel slidingly fitted in said body and the axis of which is parallel with that of said bed, a frusto-conical eccentric bore being provided in said barrel to carry the dead center, the axis of said bore being vertically spaced with reference to the axis of the barrel by a small amount such that the vertical shifting of the bore axis during a small angular adjustment of the barrel is insignificant, said sliding barrel being provided furthermore with a longitudinal groove, a fiat key slidingly engaging said groove, and projecting radially out of the latter, aligned screws located to either side of the key perpendicularly thereto and the tips of which are in contact with the opposite sides of the key, the movements of the screws in either direction by equal and opposite amounts shifting the key laterally and thereby urging the barrel into an angular rotation by a small amount and holding it fast in the angular position assumed by it.

, 5. An arrangement for adjusting the position of the dead center carrying a tool with a flat shank in a machinetool provided with a bed, comprising a dead center body adapted to be rigidly and directly secured to the bed of the machine-tool, a barrel slidingly fitted in said body and the axis of which is parallel with that of said bed, a frusto-conical eccentric bore being provided in said barrel to carry the dead center, said sliding barrel being provided furthermore with a longitudinal groove and with a further bore coaxial with the barrel and opening into said frusto-conical bore and adapted to hold against rotation the tool carried by the dead center fitted in the frustoconical bore through engagement of the flat shank of said tool with the coaxial bore, a fiat key slidingly engaging said groove, and projecting radially out of the latter, aligned screws located to either side of the key perpendicularly thereto and the tips of which are in contact with the opposite sides of the key, the movements of the screws in either direction by equal and opposite amounts shifting the key laterally and thereby urging the barrel into an angular rotation by a small amount and holding it fast in the angular position assumed by it.

References Cited in the file of this patent UNITED STATES PATENTS 1,387,622 Simmons et al Aug. 16, 1921 

